THE  SYSTEMATIC  DEVELOPMENT 

OF  X-RAY 
PLATES  AND  FILMS 


THE 

SYSTEMATIC  DEVELOPMENT 

OF 

X-EAY  PLATES  AND  FILMS 


BY 

LEHMAN  WENDELL,  B.S.,  D.D.S. 

CHIEF     OF     THE     PHOTOGRAPHIC     WORK,     INSTRUCTOR     OF     PROSTHETICS     AND 
ORTHODONTIA,     COLLEGE    OF    DENTISTRY,    UNIVERSITY    OF    MINNESOTA 


ILLUSTRATED 


ST.  LOUIS 
C.  V.  MOSBY  COMPANY 

1919 


v 
1 


COPYRIGHT,   1919,  BY  C.  "V.   MOSBY  COMPANY 


Press  of 

C.     V.    Mosby    Company 
St.   Louis 


PREFACE 

This  book  has  been  Avritten  in  the  hope  that  it  will 
throw  some  needed  light  upon  a  much  neglected  branch 
of  radiography.  Little  has  been  written  upon  the  pho- 
tographic phase  of  radiography,  and  the  few  pages  that 
have  appeared  are  antiquated.  It  is  a  fact  that  few 
radiographers  pay  sufficient  attention  to  the  develop- 
ment of  the  x-ray  film  or  plate,  and  even  many  of  the 
so-called  experts  produce  pictures  which,  considered 
from  a  purely  photographic  point  of  view,  can  be  classed 
only  as  amateurish.  The  radiographer  should  be  just 
as  painstaking  in  the  development  of  his  pictures  as  the 
professional  photographer,  and  unless  he  is  willing  to 
adopt  a  method  which  will  eliminate  the  element  of 
chance,  he  can  never  hope  for  uniformity  of  results. 

In  preparing  this  book  I  have  at  all  times  kept  in 
mind  the  fact  that  the  book  will  be  largely  read  by  the 
assistant,  who,  perhaps,  lacks  a  technical  education.  The 
book  has  therefore  been  made  as  nontechnical  as  possi- 
ble, and  even  the  layman  can  read  it  with  understanding. 

I  wish  to  lay  special  stress  upon  that  portion  of  Chap- 
ter III  which  deals  with  the  tank  or  stand  method  of  de- 
velopment. The  tank  has  fully  proved  its  worth,  both 
from  a  scientific  and  from  a  practical  point  of  view,  and 
there  is  no  question  but  that  the  tank  method  is  best 
suited  for  the  worker  whose  knowledge  of  photography 
is  limited. 

The  need  of  illustrative  material  for  lectures  has  be- 
come so  urgent  among  professional  men  that  I  deemed 
it  advisable  to  add  a  brief  chapter  on  the  making  of 
lantern  slides  from  x-ray  films  or  plates.  While  slide 
making  is  very  exacting,  there  is  nothing  unduly  difficult 

5 


j,  PEEFACE 

about  it,  and  the  practitioner  who  is  able  to  produce  a 
good  radiogram  should  find  no  difficulty  in  making  a 
satisfactory  slide. 

Many  of  the  radiographic  illustrations  in  these  pages 
will  prove  disappointing,  because  of  the  fact  that  the 
gradation  and  delicate  details  so  often  referred  to  in  the 
text  are  largely  absent.  This  is  due  not  to  faulty  x-ray 
or  photographic  work,  but  to  the  inherent  limitations  of 
the  halftone  process  of  engraving.  A  halftone  reproduc- 
tion always  loses  at  both  ends  of  the  scale,  the  whites 
becoming  darker  in  tone,  and  the  blacks  lighter.  If  this 
fact  is  kept  in  mind  when  viewing  book  illustrations  in 
general,  much  confusion  and  perhaps  unjust  criticism 
may  be  avoided. 

LEHMAN  WENDELL. 

University  of  Minnesota, 
Minneapolis,  Minn. 


CONTENTS 


CHAPTEE  I 

PAGE 

INTRODUCTORY 11 

CHAPTER  II 

FUNDAMENTALS 13 

The   X-ray  Plate 13 

Basic   Principles   of   Development 16 

Fixation 19 

CHAPTEE  III 

METHODS     or     DEVELOPMENT 20 

Tray,  or  Visual  Inspection,   Method 20 

Factorial  Method 29 

Tank,    or    Stand,    Development 31 

CHAPTEE  IV 

DEVELOPING   FORMULAS 35 

Hydrochiiion    Formula 35 

Metol-hydrochinori    Formula 35 

The  Fixing  Bath 36 

Plain   Acid   Fixing   Bath 37 

Acid  Fixing  Bath 37 

Chrome    Alum    Fixing    Bath 38 

Washing 38 

Drying   the    Negative 38 

CHAPTEE  V 

ALTERATION  OF  THE  NEGATIVE  BY  CHEMICAL  MEANS 41 

Intensification 41 

Eeductioii 44 

Persulphate  Eeducer 48 

7 


8  CONTENTS 

CHAPTER  VI 

TANKS 49 

Plate  Tanks 49 

Film  Tanks 50 

The  Author's  Tanks  for  Dental  Films 55 

The   Care  of   Tanks 56 

The  Tank  as  a  Standard 56 

Controlling  the  Temperature  of  the  Solutions 57 

Specification  of  Water-Bath  for  X-Ray  Developing 58 

CHAPTER  VII 

A  WORD  ON  CHEMICALS 60 

Solid  Matter  in  Alkaline  Solutions 61 

CHAPTER  VIII 

USEFUL  SUGGESTIONS 63 

Weights  and  Measures 63 

Weights    and    Parts     .     .     .     . 65 

Percentage    Solutions        65 

CHAPTER  IX 

THE  DARKROOM 66 

Testing  the  Darkroom  Light 68 

CHAPTER  X 

LANTERN  S.LIDE  MAKING 69 

Contact  Printing 69 

Printing  by  Projection 70 

Lantern  Slides  from  X-ray  Negatives ...  72 

The   Direct    Method 72 

The   Indirect   Method  73 


ILLUSTRATIONS 


FIGURE  PAGE 

1.  An  x-ray  made  with  an  x-ray  plate 14 

2.  An  x-ray  made  with  an  ordinary  photographic  plate 15 

3.  Film   developed  with  too   cold   a   solution 23 

4.  Film  developed  with  normal  solution 23 

5.  Film  developed  with  too  warm  a  solution 23 

6.  Film  developed  with  very  cold  solution 23 

7.  Film  developed  with  normal  solution 23 

8.  Film   developed  with  very  warm   solution 23 

9.  Overexposed  and  underdeveloped  negative 33 

10.  Overexposed,  correctly  developed,  and  reduced  negative     ....  33 

11.  Negative   rack 39 

12.  Film   clip 39 

13.  Simple  method  of  drying 40 

14.  Underexposed  negative,  correctly  developed 42 

15.  The  same  after  intensification 43 

16.  Overexposed  negative,  correctly  developed 46 

17.  The  same  after  reduction 47 

18.  Plate  tank  and  cage 50 

19.  Film   tank 51 

20.  Tubes  for  holding  pairs  of  films ,    ....  51 

21.  Film  tank  with  tubes  in  place 52 

22.  Two  types  of  thermometers 53 

23.  The  author's  tanks  for  developing  dental  films 54 

24.  A  metal  sink  for  use  with  the  "unit"  system .     .  55 

25.  A   constant   temperature   bath 58 

26.  Photographic   scale 64 

27.  Diagram  for  darkroom 67 

28.  Lantern   slide   camera 71 

29.  Another   type   of   lantern   slide   camera 7L 

30.  Lantern  slide  by  the  direct  method 72 

31.  Method  of  producing  the  master  positive 73 

32.  The  master  positive 74 

33.  Lantern  slide  from  the  master  positive 75 

9 


10  ILLUSTKATIONS 

PLATE  PAGE 

I.  Overexposed  films  developed  with  too  warm  a  solution     ....  21 

II.  Overexposed  and  very  much  underdeveloped  films 25 

III.  Extreme  examples  of  poor  radiograms 26 

IV.  Overexposed  and  very  much  underdeveloped  radiograms     ....  27 


SYSTEMATIC  DEVELOPMENT  OF  X-RAY 
PLATES  AND  FILMS 


CHAPTER  I 

INTRODUCTORY 

Considering  the  widespread  use  of  radiograms  one 
notes  with  surprise  how  few  of  the  countless  numbers 
produced  are  completely  satisfactory.  Many  of  them 
bear  evidence  of  having  been  taken  with  a  faulty  or  in- 
ferior machine,  others  have  been  taken  at  a  wrong  angle 
and  are  so  badly  distorted  that  they  do  not  present  the 
anatomic  relations  at  all  truthfully;  the  vast  majority, 
however,  are  bad  from  a  photographic  point  of  view,  and 
a  film  or  plate  that  is  bad  photographically  is  more  or  less 
unreliable  for  diagnostic  purposes.  So  universal  is  this 
last-named  fault  that  there  can  be  no  doubt  but  that  the 
majority  of  operators  fail  in  one  or  more  of  the  funda- 
mental principles  of  photography,  and  the  efficiency 
which  their  knowledge  of  radiography  should  give  them 
is  lost  by  faulty  photographic  work.  Many  seem  to  think 
that  proficiency  in  handling  the  x-ray  machine  is  all  that 
is  necessary,  the  development  of  the  exposed  film  or 
plate  being  so  simple  and  automatic  a  process  that  it 
would  be  foolish  for  the  operator  himself  to  waste  any 
time  over  it.  But  that  is  a  mistake.  It  is  like  a  man 
who,  knowing  nothing  about  photography,  purchases  a 
very  expensive  camera,  in  the  belief  that  the  anastig- 
matic  lens  and  the  elaborate  accessories  will  compensate 
for  his  lack  of  knowledge  of  photography. 

An  interesting  story  is  told  by  Mr.  Otto  Doehn,  of  the 
X-ray  Department  of  the  Eastman  Kodak  Company, 
and  since  it  has  a  direct  bearing  upon  what  has  already 

11 


12  DEVELOPMENT    OF   X-EAY   PLATES   AND   FILMS 

been  said  I  take  the  liberty  of  putting  it  in  print.  In  one 
of  our  large  eastern  cities  a  number  of  wealthy  and  phil- 
anthropic men  erected  a  beautiful  and  thoroughly  mod- 
ern hospital,  and  in  order  that  it  should  rank  second  to 
none,  the  best  physicians  available  were  chosen  for  the 
various  departments.  A  promising  young  man  was  se- 
lected for  the  radiographic  department.  He  prepared 
himelf  by  taking  a  special  course  in  the  subject  in  this 
country,  then  went  to  Europe  and  made  a  thorough 
study  of  radiography  there.  When  he  finally  returned 
to  take  up  his  work  he  felt  competent  to  handle  anything 
pertaining  to  x-ray  work.  Several  weeks  after  he  had 
taken  charge  of  his  department  Mr.  Doelm  paid  him  a 
visit,  and,  to  use  the  words  of  the  visitor  himself,  the 
radiographer  was  the  sickest  looking  man  he  had  ever 
seen.  He  was  thoroughly  familiar  with  his  machine,  and 
handled  it  with  ease  and  certainty;  yet,  the  pictures 
which  he  produced  were  practically  worthless.  He  had 
just  exposed  an  8x10  plate  which  he  placed  in  the  devel- 
oping tank  at  the  moment  Mr.  Doehn  entered.  Unob- 
served by  the  radiographer,  Mr.  Doehn  took  .out  his 
watch  to  time  the  development.  Fifteen  minutes  passed, 
and  Mr.  Doehn  became  restless  because  he  knew  that 
more  than  enough  time  had  elapsed  to  produce  a  fully 
developed  plate.  Twenty  minutes  passed  and  Mr.  Doehn 
asked  the  radiographer  if  he  hadn't  forgotten  his  plate. 
"No,"  said  the  latter,  "it  will  take  another  ten  minutes." 
At  the  end  of  the  half  hour  the  plate  was  removed  from 
the  tank  and  it  was  hopelessly  bad.  Mr.  Doehn  tested 
the  temperature  of  the  developer  and  found  that  it  was 
a  trifle  under  60°  F.  Now,  hydrochinon,  one  of  the 
chief  agents  in  an  x-ray  developer,  almost  ceases  to  op- 
perate  below  60  degrees.  The  radiographer  had  over- 
exposed his  plate  considerably  and  then  tried  to  force  an 
image  out  of  it  with  a  developer  which  was  too  cold  to 
produce  the  desired  chemical  reaction. 


CHAPTER  II 

FUNDAMENTALS 

The  X-ray  Plate* 

The  sensitive  part  of  the  plate  or  film,  called  the  emul- 
sion, consists  of  a  layer,  about  one-thousandth  of  an  inch 
thick,  of  gelatine  impregnated  with  silver  bromide  salts. 
The  emulsion  may  be  coated  on  glass  and  we  have  the 
photographic  plate,  or  it  may  be  coated  on  a  thin  cellu- 
loid base  and  wre  have  the  photographic  film.  When  the 
x-rays,  or  light,  or  other  types  of  radiation,  strike  the 
sensitive  emulsion,  an  image  is  produced  upon  it.  The 
image,  however,  is  latent  or  invisible  and  must  be  made 
visible  by  chemical  means. 

The  idea  is  quite  prevalent  that  the  x-ray  plate  differs 
in  some  mysterious  manner  from  the  ordinary  photo- 
graphic plate.  There  is  a  difference,  to  be  sure,  but  it  is 
not  so  great  as  one  might  imagine.  Both  plates  are 
coated  with  a  gelatine  emulsion  charged  with  silver  bro- 
mide, and  from  the  standpoint  of  thickness  the  emulsion 
is  approximately  the  same.  All  x-ray  emulsions,  how- 
ever, contain  silver  bromide  in  a  more  concentrated  form. 
As  regards  speed,  the  x-ray  emulsion  when  exposed  to 
white  light  is  approximately  from  one-third  to  one-half 
slower  than  ordinary  kodak  speed  film.  There  is  also  an 
increase  of  contrast  in  x-ray  plates  over  ordinary  plates. 
This  is  necessary  because  the  tissues  of  the  human  body 
are  often  nearly  as  opaque  as  the  material  of  which  it 
is  desired  to  obtain  an  outline,  and  a  soft-working  plate 
would  frequently  result  in  no  differentiation  of  parts. 
Again,  x-ray  plates  are  not  sensitive  to  a  full  range  of 

*For  the  sake  of  brevity,  the  word  plate  will  be  used  almost  exclusively  in  these 
pages,  but  it  should  be  borne  in  mind  that  what  is  said  of  plates  may  also  be  said  of 
films,  and  the  two  words  can,  in  the  majority  of  instances,  be  used  interchangeably. 

13 


14  DEVELOPMENT    OF    X-EAY   PLATES    AND    FILMS 


Fig.   1. 


FUNDAMENTALS 


15 


Fig    2. 


16  DEVELOPMENT    OF    X-RAY    PLATES   AND    FILMS 

colors  because  in  x-ray  work  we  deal  with  practically  no 
colors.  Such  plates  are,  therefore,  non-color-sensitive, 
or  non-o rthochromatic,  using  the  technical  term.  Ordi- 
nary photographic  plates,  on  the  other  hand,  must  be  able 
to  record  the  colors  of  the  spectrum,  and  such  color-sen- 
sitive plates  are  known  as  orthochromatic. 

In  order  to  illustrate  graphically  the  difference  be- 
tween the  x-ray  plate  and  the  ordinary  photographic 
plate  two  negatives  were  made,  one  (Fig.  1)  on  an  x-ray 
plate,  the  other  (Fig.  2)  on  an  ordinary  Non-halation  L 
Ortho  Plate.  Both  were  exposed  for  the  same  length  of 
time,  and  were  developed  in  the  same  solution  for  the 
same  length  of  time.  As  will  be  seen,  the  results  are 
practically  identical. 

Basic  Principles  of  Development 

Complex  theories  of  development  do  not  interest  the 
radiographer  so  much  as  a  direct  method  for  producing 
the  highest  average  of  good  results.  It  is,  however,  es- 
sential that  he  possess  a  knowledge  of  the  fundamental 
principles  of  development,  and  the  laAvs  governing  the 
various  chemicals  composing  the  developer,  for  without 
this  knowledge  it  is  extremely  difficult,  if  not  impossible 
to  locate  and  correct  errors  of  development. 

The  moment  we  place  the  exposed  plate  in  the  devel- 
oper the  image  gradually  appears,  and  it  seems  as 
though  the  developer  were  adding  something  to  the  plate, 
but  this  is  not  the  case.  A  developer  is  what  is  known  in 
chemistry  as  a  "reducing  agent,"  and  it  plays  the  same 
part  for  the  exposed  silver  bromide  that  the  coke  of  the 
blast  furnace  plays  for  the  iron  ore.  When  iron  ore  is 
smelted  with  coke  in  a  blast  furnace,  the  coke  takes  away 
the  foreign  matter  which  is  combined  with  the  iron  and 
leaves  the  pure  metallic  iron,  and  this  process  is  called 
the  "reduction"  of  the  ore.  In  the  same  way  the  devel- 
oper takes  away  from  the  silver  bromide  the  bromide 


FUNDAMENTALS  17 

which  is  combined  with  the  silver  and  leaves  behind  the 
metallic  silver. 

The  image  which  the  developing  solution  has  brought 
out  upon  the  plate  appears  black  because  the  grains  of 
metallic  silver  are  small  and  irregular  in  shape.  _W_e 
think  of  silver  as  a  white  metal,  but  if  we  break  it  up  into 
minute  particles,  they  will  appear  grey,  and  the  grains 
of  silver  in  the  plate  are  so  spongy  in  their  nature  that 
they  appear  quite  black. 

There  are  many  reducing  agents  available  in  chemis- 
try, but  only  a  limited  number  can  be  used  for  photo- 
graphic purposes,  because  while  they  must  be  strong 
enough  to  reduce  the  exposed  silver  bromide,  yet,  if 
they  are  too  strong,  they  will  also  attack  the  silver  bro- 
mide which  has  not  been  acted  upon  by  the  x-rays. 

The  best  reducing  agents  for  x-ray  plates  are  metol* 
and  liydrocliinon,  usually  used  in  combination.  Metol- 
hydrochinon  is  not  sufficiently  energetic  to  penetrate  the 
emulsion,  and  so  some  chemical  which  has  the  power  to 
open  the  pores  of  the  gelatine  and  allow  the  reducing 
agents  to  penetrate  and  do  their  work  must  be  added. 
This  is  an  alkali,  usually  carbonate  of  soda.  It  is  spoken 
of  as  the  accelerator,  because  it  accelerates,  or  hastens, 
the  actionoT  the  reducing  agent.  The  developer  as  it 
now  stands  has  a  great  affinity  for  the  oxygen  of  the  air, 
and  if  no  other  chemical  were  added  it  Avould  soon  oxi- 
dize and  lose  its  reducing  power.  Therefore,  sulphite 
of  soda,  a  chemical  which  has  a  great  eagerness  Tor  the 
air  without  hindering  the  work  of  the  other  chemicals,  is 
added.  Lastly,  a  developer  containing  the  two  reducing 
agents,  the  alkali,  and  the  sulphite  may  be  so  strong  that 
there  is  some  danger  that  it  will  produce  a  chemical  fog 
over  the  entire  film  and  so  to  restrain  the  activity  of  the 

*Metol  is  a  German  product  and  was  the  standard  developer  for  many  years.  It  is 
not  available  at  the  present  time,  but  there  are  many  substitutes  which  work  equally 
well.  Among  the  best  may  be  mentioned  elon,  rhodol,  monomet,  photol,  serchol, 
phenomet. 


18  DEVELOPMENT    OF    X-RAY    PLATES    AXD    FILMS 

developer  a  few  grains  of  bromide   of  potassium  are 
added. 

The  typical  x-ray  developer  may  therefore  be  tabu- 
lated as  follows : 

1.  The  reducing  agent  Metol-hydrochinon. 

2.  The   accelerator  Carbonate   of  Soda. 

3.  The  preservative  Sulphite  of  Soda 

4.  The  restrainer  Bromide  of  Potassium 

When  the  plate  is  placed  in  such  a  developer  the  so- 
lution penetrates  the  gelatine  and  attacks  the  exposed 
grains  of  silver  bromide  and  converts  them  into  black 
grains  of  metallic  silver,  thus  forming  an  image  upon  the 
plate.  As  action  proceeds  the  developer  which  has  pene- 
trated the  gelatine  oxidizes,  and,  having  lost  its  reducing 
power,  is  diffused  out  from  the  gelatine,  and  its  place 
is  taken  by  fresh  developer,  so  that  a  constant  supply 
of  fresh  solution  is  going  to  the  grains  of  silver  bromide. 
Development,  therefore,  takes  a  certain  definite  time,  the 
image  increasing  in  density  as  the  time  goes  on.  Enough 
time  must  be  given  for  the  developer  to  do  its  work,  but 
if  the  plate  is  left  in  too  long  it  will  be  overdeveloped ; 
in  other  words,  so  much  of  the  silver  bromide  will  be 
reduced  to  metallic  silver  that  not  only  will  the  image 
become  too  dense,  but  a  chemical  fog  may  spread  over 
the  entire  plate.  On  the  other  hand,  if  the  plate  is  not 
developed  for  a  sufficient  length  of  time,  it  will  be  un- 
derdeveloped ;  that  is  to  say,  only  the  superficial  portion 
of  silver  bromide  granules  will  be  converted  into  metallic 
silver,  while  the  underlying  portion  will  not  be  acted 
upon  at  all  by  the  developer  and  will  subsequently  be  dis- 
solved by  the  fixing  bath.  We  are  told  by  one  of  the 
largest  plate  manufacturers  in  the  country  that  thou- 
sands of  dollars  worth  of  silver  is  thus  wasted  annually. 
Most  radiographers  liave  a  tendency  to  under  develop 
their  plates. 


FUNDAMENTALS  19 

Fixation 

After  the  plate  has  been  developed,  which  is  one  chem- 
ical process,  another  chemical  process  must  take  place 
before  the  negative  is  complete ;  that  is,  the  plate  must  be 
"fixed,"  to  remove  unused  material  and  to  make  the 
image  permanent.  Before  using  apparatus  in  any  chem- 
ical operation,  the  rule  is  that  it  should  be  thoroughly 
washed.  The  same  holds  good  with  regard  to  the  photo- 
graphic plate.  It  should  be  thoroughly  rinsed  after  the 
first  chemical  process  (developing),  before  the  second 
chemical  process  (fixing)  is  performed. 

The  chief  ingredient  of  the  fixing  bath  is  hyposulphite 
of  soda  (commonly  called  liypo}.  It  has  the  power  of 
fixing  the  metallic  image,  while  at  the  same  time  render- 
ing the  unexposed  silver  bromide  into  a  soluble  com- 
pound which  is  finally  removed  in  the  wash  water. 

Fixing  will  usually  bo  completed  in  from  ten  to  twenty 
minutes,  but  if  the  plates  are  left  in  longer  no  harm  will 
be  done.  Fixation  should  in  all  cases  be  double  the  time 
it  takes  to  remove  the  milky  deposit. 


CHAPTER  III 

METHODS  OF  DEVELOPMENT 

In  the  latter  part  of  the  preceding  chapter  we  spoke 
of  the  chemical  composition  of  the  x-ray  plate  and  of 
the  general  action  of  the  photographic  developer  upon 
it.  We  arc  now  ready  to  discuss  the  various  methods 
employed  for  bringing  out  the  latent  image  upon  the 
exposed  plate.  Three  methods  or  systems  of  develop- 
ing a  photographic  plate  are  in  common  use.  The  first 
may  be  called  the  Tray,  or  Visual  Inspection,  Method, 
the  second  the  Factorial  Method,  and  the  third  the  Tank, 
or  Stand,  Method. 

Tray,  or  Visual  Inspection,  Method 

By  the  tray  or  visual  inspection,  method  is  meant  a 
method  wherein  the  worker  watches  the  plate  or  film  as 
it  develops,  and  judges  the  completion  of  development  by 
the  appearance  of  the  negative. 

It  is  a  curious  fact  that  this  method  is  practiced  by 
two  classes  of  workers— the  most  advanced,  and  the  least 
advanced.  It  is  the  system  that  some  of  the  most  ex- 
perienced photographic  workers  employ,  and  it  is  the 
system  by  which  the  veriest  tyro  in  matters  photographic 
will  try  to  coax  an  image  out  of  a  reluctant  plate.  It  is 
the  system  almost  universally  employed  by  radiograph- 
ers, because  of  its  seeming  simplicity.  However,  the 
simplicity  is  only  apparent,  not  real.  In  fact,  far  from 
being  a  simple  method  it  is  the  most  difficult  of  all  meth- 
ods, and  to  master  it  requires  first  of  all  a  thorough 
knowledge  of  photography,  and  secondly  years  of  prac- 
tical application.  The  worker  who  follows  these  methods 
places  the  exposed  plate  in  the  developing  dish,  and  flows 

20 


METHODS    OF    DEVELOPMENT 


21 


PLATE  I 

Examples  of  overexposed  films  developed  with  too  warm  a  solution.  Note  the 
dense,  muddy  results,  the  detail  and  gradation  being  wholly  or  partly  obscured.  These 
pictures  were  all  chosen  from  the  daily  output  of  a  large  hospital. 


22  DEVELOPMENT    OF    X-EAY   PLATES   AND    FILMS 

the  developer  over  it,  or  in  the  case  of  small  dental  films, 
the  tray  is  filled  with  the  solution  and  the  films  sub- 
merged in  it.  From  time  to  time  the  plate  is  removed 
from  the  dish,  and  an  attempt  made  to  look  through  it 
by  the  light  of  the  red  lamp,  and  to  form  a  judgment  as 
to  how  far  development  has  proceeded.  This  sounds 
like  simplicity  itself,  and  so  it  is  when  one  knows  how  to 
do  it,  but  until  one  does,  it  is  the  reverse.  It  will  be 
found  that  considerable  experience  is  needed  before  one 
can  with  certainty  decide  that  a  negative  is  or  is  not  fully 
developed.  The  negative  is  practically  opaque  before  it 
goes  through  the  fixing  bath  and  even  if  it  were  to  be 
examined  in  broad  daylight  it  would  be  difficult  to  judge 
the  density. 

The  most  glaring  mistake  that  the  radiographer  makes 
when  he  employs  the  tray  method  is  that  he  pays  not  the 
slightest  heed  to  the  temperature  of  his  solution.  He 
fills  his  tray  from  a  bottle  of  stock  solution  and,  for  all 
he  knows,  the  temperature  of  the  bath  may  be  60°  or  70° 
or  90°.  With  too  cold  or  too  warm  a  developer  he  may 
produce  a  negative  which  will  appear  correct  when 
viewed  before  the  red  light,  but  the  finished  product  will 
not  be  correct.  If,  for  instance,  a  perfectly  developed 
negative  is  obtained  when  a  certain  degree  of  opacity  is 
observed  at  65°  F.  this  same  degree  of  opacity  (as  ob- 
served before  the  darkroom  light)  would  yield  an  under- 
developed negative  at  60°  F.  and  an  overdeveloped  neg- 
ative at  75°  F.  In  other  words,  three  plates  developed 
at  varying  temperatures  (60°,  65°,  75°)  can  be  developed 
to  a  point  where  the  opacity  will  appear  to  be  identical 
when  viewed  before  the  red  light  but  when  these  same 
plates  have  been  fixed,  washed,  and  dried  it  will  be  found 
that  only  that  plate  which  was  developed  at  65°  F.  is 
perfect,  the  other  two  being  inferior  as  regards  bril- 
liancy, detail,  and  gradation. 

A  comparison  of  Figs.  3,  4,  and  5  will  make  the  point 
clear.  All  three  pictures  were  exposed  normally  and 


METHODS    OF    DEVELOPMENT 


23 


simultaneously;  that  is,  the  three  films  were  placed  in 
the  same  container  and  given  an  exposure  of  two  sec- 
onds. The  films  w^ere  next  developed  in  solutions  of 
varying  temperatures ;  Fig.  3  being  developed  at  60°  F., 


Fig.   3. 


Fig.  4. 


Fig    6. 


Fig.   7. 


Fig. 


Fig.  4,  at  65°  F.  (normal),  and  Fig.  5,  at  75°  F.  Devel- 
opment proceeded  in  each  case  until  the  opacity  of  the 
image  seemed  correct  when  examined  before  the  dark- 
room light.  What  was  the  result?  Fig.  3  shows  a  weak 


24  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

image,  lacking  in  brilliancy  and  detail,  and  for  diagnostic 
purposes  the  picture  is  practically  worthless.  Fig.  4 
was  developed  at  a  normal  temperature  (65°  F.).  The 
picture  is  rich  in  gradation  and  shows  as  much  detail 
as  could  possibly  be  got  out  of  a  picture  of  that  kind. 
Fig.  5,  while  far  superior  to  Fig.  3,  shows  a  slight  muddy 
appearance.  Had  the  temperature  been  80°  F.  instead 
of  75°  F.,  a  not  uncommon  temperature  during  hot 
weather,  the  muddiness  would  have  been  pronounced  and 
would  practically  have  obscured  the  details. 

In  a  number  of  x-ray  darkrooms  we  have  actually 
found  the  temperature  of  the  developer  as  low  as  50°  F. 
in  winter  and  as  high  as  80°  F.  in  summer.  Let  us  see 
just  what  effect  such  an  extreme  of  temperature  would 
have  upon  normally  exposed  films,  the  developing  agent 
being  hydrochinone. 

Fig.  6  was  developed  at  a  temperature  of  50°  F.  With 
a  concentrated  solution,  such  as  is  used  for  x-ray  work, 
full  density  of  the  negative  should  be  obtained  in  seven 
minutes.  In  this  instance  there  was  practically  no  visi- 
ble chemical  reaction  in  that  time.  Development  was 
therefore  continued  for  another  seven  minutes  with  al- 
most the  same  result,  and  it  was  finally  lengthened  to 
twenty  minutes,  or  three  times  the  normal.  The  result 
is  a  thin,  transparent  negative  with  so  little  detail  that 
it  is  worthless  for  diagnostic  purposes.  What  was  the 
reason!  Simply  this,  that  hydrochinone  practically 
ceases  to  operate  below  60°  F.,  and  even  prolonged  de- 
velopment produces  but  a  slight  chemical  reaction. 
Many  operators  who  are  in  the  habit  of  using  a  cold  de- 
veloper are  led  to  believe  that  their  thin  negatives  are 
the  result  of  underexposure,  and  in  the  hope  of  bring- 
ing an  image  out  of  the  film  the  exposure  is  increased 
tremendously. 

Fig.  7  was  produced  under  normal  conditions  through- 
out. The  time  of  exposure  was  the  same  as  for  Figs. 
6  and  8,  namely,  two  seconds.  The  temperature  of  the 


METHODS    OF    DEVELOPMENT 


25 


PLATE  II 

Examples  of  badly  overexposed  and  very  much  underdeveloped  films.  Note  lack 
of  detail,  contrast,  and  gradation.  These  pictures  were  all  taken  from  the  daily  out- 
put of  a  large  institution  where  the  tray  method  of  development  is  used  and  where 
the  temperature  of  the  solution  is  never  taken. 


26  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 


PLATE  III 

Extreme  examples  of  poor  radiograms  which  were  actually  submitted  to  a  dentist 
for  diagnostic  purposes.  All  were  badly  overexposed,  development  was  improper,  and 
fixation  was  imperfectly  carried  out,  resulting  in  badly  stained  negatives.  Worst  of 
all,  the  films  were  so  carelessly  handled  that  all  are  light  struck. 


METHODS    OF    DEVELOPMENT 


27 


It 


.x 


t 


•0- 


IV 

Another    group    of    overexposed    and    very    much    underdeveloped    radiograms.    De- 
veloped by  the  tray   method,   temperature   of   solution  being  unknown. 


28  DEVELOPMENT    OF   X-RAY   PLATES   AND   FILMS 

developer  was  65°  F.  and  the  time  of  development  was 
seven  minutes.  The  result  is  a  negative  with  sufficient 
detail,  gradation  and  contrast  to  form  a  reliable  picture 
for  diagnostic  purposes. 

In  Fig.  8  we  have  a  picture  which  was  correctly  ex- 
posed and  developed  for  the  prescribed  length  of  time, 
but  the  developer  was  too  warm  (80°  F.),  and  the  result 
is  a  dense,  muddy  picture  in  which  the  details  are 
clogged  by  the  general  opacity.  The  excessive  opacity 
could  have  been  avoided  by  shortening  the  development, 
but  this  would  have  resulted  in  loss  of  detail. 

In  view  of  the  foregoing,  the  tray,  or  visual  inspection, 
method  is  not  to  be  recommended  for  radiographic  work, 
unless  the  operator  is  willing  to  heed  the  advice  of  those 
who  understand  the  method  and  will  follow  their  in- 
structions implicitly.  The  tray  method  as  employed  by 
the  vast  majority  of  radiographers  is  not  only  unrelia- 
ble and  unsatisfactory,  but  wholly  unscientific. 

Should  the  radiographer,  however,  insist  on  using  the 
tray  method,  let  him  observe  the  following  simple  rules : 

1.  Keep  the  developer  at  a  temperature  of  65°  F.. 

2.  Develop  for  a  definite  length  of  time  regardless  of 
exposure,  correcting  errors  of  exposure  by  reduction  or 
intensification  (see  Chapter  V). 

3.  Rock  the  tray  during  development,  constantly  and 
in  both  directions.    If  this  is  not  done  there  may  be  a 
general  mottling  all  over  the  plate.    There  is  no  remedy ; 
prevention  is  easy. 

4.  Always  use  the  same  trays  for  the  same  purposes, — 
one  tray  for  the  developer,  one  for  the  fixing  bath. 

5.  Wash  trays  before  and  after  using. 

6.  Patches  of  fog  may  come  from  fingers  that  are  con- 
taminated with  hypo.    Even  a  trace  of  hypo  in  the  devel- 
oper will  affect  its  working  qualities.     Strive  for  abso- 
lute cleanliness. 

In  order  that  the  radiographer  may  fully  realize  the 
importance  of  rule  No.  3  let  us  discuss  this  more  in  de- 


METHODS   OF   DEVELOPMENT  29 

tail.  The  object  of  rocking  the  tray  is  twofold.  In  the 
first  place,  it  has  a  great  influence  on  the  vigor  and  bril- 
liancy of  the  negative,  because  the  action  of  the  devel- 
oper releases  bromine  from  the  silver  bromide  of  the 
plate,  which  bromine  immediately  combines  with  the  al- 
kali, forming  a  bromide.  Now  bromide,  as  was  pointed 
out  in  a  previous  chapter,  serves  to  restrain  the  activity 
of  the  developer,  and  if  the  additional  bromide  which 
forms  is  not  distributed  by  rocking,  it  will  remain  in 
the  developer  at  the  place  where  formed,  so  that  the  de- 
velopment at  that  part  of  the  plate  is  additionally  re- 
strained. It  will  be  easily  seen  that  the  most  bromide 
will  be  formed  and  the  greatest  restraining  action  will 
result  just  at  those  places  where  action  ought  to  be  most 
vigorous.  Less  bromide  will  be  formed  in  the  less  ex- 
posed parts.  The  latter  will  therefore  develop  more  and 
the  former  less  than  they  should,,  producing  flatness  in 
the  resulting  negative.  Another  result  of  rocking  is  to 
prevent  a  mottled  appearance,  which  often  becomes  quite 
pronounced  when  the  developer  is  not  kept  in  motion. 

Factorial  Method 

The  factorial  method  of  development  is  based  on  the 
fact  that  the  total  time  of  development  of  a  plate  bears 
a  fixed  relation  to  the  time  of  appearance  of  the  image. 
The  exposed  plate  is  put  into  the  tray,  and  the  opera- 
tor's watch  is  placed  so  that  the  second  hand  can  be 
clearly  seen.  When  it  exactly  marks  an  even  minute  the 
developer  is  quickly  flooded  over  the  plate,  and  the  dish 
covered  with  a  piece  of  cardboard  to  exclude  all  light. 
The  cover  is  removed  at  intervals  of  about  five  seconds 
and  the  plate  examined  to  see  whether  it  is  still  quite 
clear  or  white.  After  a  brief  time  an  almost  impercept- 
ible darkening  will  be  seen  here  and  there  on  the  plate. 
The  moment  this  appears,  cover  the  dish  again,  and  note 
the  exact  number  of  seconds  which  have  elapsed  since  the 


30  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

developer  was  poured  on.  Multiply  this  by  the  factorial 
number  of  the  developer  and  the  result  will  be  the  num- 
ber of  seconds  required  for  complete  development. 

For  the  sake  of  illustration  let  us  take  a  concrete  ex- 
ample. A  plate  is  exposed  for  two  seconds  and  placed 
in  a  solution  of,  say,  metol — a  developer  having  30  for 
its  factorial  number — and  the  first  trace  of  the  image  ap- 
pears in  10  seconds.  Then  the  total  time  required  for 
development  will  be  30  X  10  =  300  seconds,  or  5  minutes. 
Again,  another  plate  is  exposed  on  the  same  subject,  un- 
der identical  conditions,  for  three  seconds  and  placed  in 
the  same  strength  of  metol.  The  first  trace  of  the  image 
will  be  apparent  in  less  than  10  seconds  as  it  has  had  a 
longer  exposure  than  the  first  plate,  say  7  seconds.  Then 
the  total  time  required  for  development  will  be  30  X  7 
-  210  seconds,  or  3y2  minutes.  In  this  way  two  nega- 
tives are  produced  which  are  almost  identical. 

This  system  gives  results  which  are  extremely  accu- 
rate, as  it  takes  into  account  variations  of  exposure  and 
within  certain  limits  the  temperature  of  the  solution, 
though  the  temperature  should  be  as  nearly  normal  as 
possible.  But  it  has  one  great  drawback,  a  drawback 
which  in  my  mind  is  almost  fatal :  it  compels  the  radiog- 
rapher to  keep  close  watch  on  the  early  working  of  the 
developer.  In  order  to  distinguish  the  first  appearance 
of  the  latent  image,  we  must  place  the  dish  fairly  close  to 
the  ruby  lamp ;  we  must,  in  fact,  expose  the  plate  to  the 
deteriorating  influences  of  the  illnminant  while  it  is  ex- 
tremely sensitive. 

% 
Most  Common  Developers  with  Their  Factorial  Numbers 

Metol,  30 

Kodak  powder,  18 

Metol-hydrochinon,  14 

Pyro-metol,  9 

Pyro-soda,  4.15 

Hvdrochinon  with  bromide,  5 


METHODS    OF    DEVELOPMENT  31 

The  factorial  system  is  useful  in  that  it  eliminates  the 
element  of  chance,  thus  tending  towards  uniformity  of 
results ;  but  equally  as  good,  if  not  better,  results  may  be 
had  by  the  far  simpler  tank,  or  stand,  method;  I  would 
recommend  the  latter. 

Tank,  or  Stand,  Development 

The  tank,  or  stand,  method  is  the  ideal  method  of  de- 
veloping x-ray  plates  and  films,  and  no  radiographer 
who  has  given  it  a  thorough  trial  will  be  satisfied  with 
the  old  haphazard  tray  method,  where  the  element  of 
chance  conies  so  largely  into  play.  The  tank  method  is 
probably  more  practiced  by  photographers  today  than 
either  of  the  other  methods.  Yet,  strange  to  say,  few  ra- 
diographers have  gone  to  the  trouble  of  acquainting 
themselves  with  it,  although  it  is  the  only  method  with 
Avhich  the  worker  not  thoroughly  skilled  in  photography 
can  hope  to  produce  uniform  results. 

Tank  development  is  based  on  the  action  of  a  devel- 
oper of  a  given  strength,  for  a  given  length  of  time,  at 
a  given  temperature.  The  chief  reason  Avhy  it  gives  such 
splendid  results  is  that  the  radiographer  is  compelled  to 
know  the  temperature  of  his  developer  in  order  that  he 
may  know  when  development  should  be  stopped. 

The  idea  is  quite  prevalent  among  those  not  experi- 
enced in  photography  that  the  tank  method  can  take  care 
only  of  normally  exposed  plates,  whereas  under-  and 
over-exposures  must  necessarily  come  out  of  the  tank 
under-  and  over-developed,  as  the  case  may  be.  This  idea 
is  erroneous.  The  old  theory  that  an  underexposed  plate 
should  be  given  a  prolonged  or  forced  development,  and 
that  an  overexposed  plate  should  be  given  a  shortened 
development  is  wrong.  Let  us  see  why.  When  an  under- 
exposed plate  is  placed  in  the  developer  the  image  builds 
up  very  slowly.  The  novice  is  apt  to  prolong  the  develop- 
ment for  an  immoderately  long  time,  hoping  to  bring  out 


32  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

the  missing  detail,  but  lie  forgets  that  he  can  not  bring 
out  what  is  not  there,  or  what  the  light  has  not  impressed 
on  the  plate.  All  he  does  is  to  add  density  to  the  parts 
that  do  put  in  an  appearance,  so  that  an  underexposed 
plate  that  has  been  forced  in  the  developer  shows  con- 
trast, but  lacks  detail.  In  the  case  of  the  overexposed 
plate  what  is  the  result?  The  image  flashes  up  quickly 
and  the  whole  plate  darkens  rapidly.  The  inexperienced 
workman  is  apt  to  remove  the  plate  from  the  developer 
too  soon,  with  the  result  tliat  only  the  superficial  layer 
of  the  emulsion  lias  been  acted  upon,  and  on  fixing  he 
will  find  the  plate  very  thin  and  without  contrast,  and 
almost  useless. 

Now,  what  would  happen  if  under-,  over-,  and  nor- 
mally exposed  plates  were  developed  at  the  same  time  in 
a  tank?  The  underexposed  plate  would  be  thin,  not  too 
contrasty,  and  would  have  all  the  detail  possible.  The 
overexposed  plate  would  be  dense,  but  full  of  detail  and 
gradation.  The  normally  exposed  plate  would,  of  course 
be  normal  in  every  respect.  We  may  then  formulate  the 
following  rule:  all  plates  should  be  developed  for  the 
same  length  of  time,  regardless  of  exposure.  It  is  true 
that  the  professional  photographer  does  not  follow  such 
a  rule,  but  we  must  remember  that  the  professional  pho- 
tographer has  had  years  of  experience  in  matters  photo- 
graphic and  knows  exactly  what  will  happen  when  he 
departs  from  the  normal.  The  radiographer,  on  the 
other  hand,  is  not  likely  to  be  a  skilled  photographer  and 
for  that  reason  I  strongly  recommend  that  he  standard- 
ize the  development,  making  it  mechanical,  rather  than 
relying  upon  his  own  judgment.  Development  should, 
therefore,  proceed  for  a  definite  length  of  time.  If  that 
rule  is  followed,  thin  negatives  will  at  once  indicate  un- 
derexposure; dense  negatives  overexposure,  and  such 
negatives  should  be  corrected  after  development  by  in- 
tensification or  reduction.  This  process  will  be  discussed 


METHODS    OF    DEVELOPMENT  33 

more  fully  in  a  later  chapter,  but  it  may  be  well  to  touch 
upon  it  here. 

As  previously  stated,  if  an  overexposed  negative  is 
developed  by  the  visual  inspection  (tray)  method  the 
image  will  appear  sufficiently  dense  long  before  a  com- 
plete chemical  reaction  has  taken  place,  so  there  is  al- 
ways danger  of  underdeveloping  such  a  plate. 

Fig.  9  represents  a  negative  which  was  badly  overex- 
posed, then  developed  by  the  tray  method  to  a  point 
where  the  opacity  seemed  correct,  as  judged  by  the  dark- 
room light.  The  opacity,  however,  was  only  superficial, 


Fig    9.  Fig.   10. 

the  deeper  layer  of  the  emulsion  being  untouched  by  the 
developer,  and  when  the  negative  was  placed  in  the  fix- 
ing bath  the  undeveloped  silver  bromide  was  dissolved 
and  finally  washed  away  under  the  tap.  The  result  is 
a  thin  negative,  lacking  detail,  brilliancy  and  contrast. 
Fig.  10  shows  a  negative  which  received  the  same  ex- 
posure as  Fig.  9.  In  this  case  development  was  carried 
to  its  logical  end  and  the  result  was  a  negative  so  dense 
that  transmitted  light  would  scarcely  penetrate  it.  The 
negative  was  fixed  in  the  usual  manner,  then  placed  for 
a  brief  time  in  the  reducing  bath  described  in  Chapter 


34  DEVELOPMENT    OF    X-RAY    PLATES   AND    FILMS 

V,  and  the  result  was  a  negative  wliicli  is  normal  in  every 
respect. 

Tank  development  lias  many  advantages  from  the 
standpoint  of  comfort,  convenience,  and  results,  and  that 
it  is  the  most  efficient  method  for  the  radiographer  there 
can  be  no  donbt. 

No  better  reasons  can  be  given  for  the  adoption  of  the 
tank  method  than  those  in  "Photo  Miniature,"  credited 
to  Mr.  A.  Child  Bayley: 

1.  It  gives  us  perfectly  uniform  negatives  when  ex- 
posure has  been  correct,  whether  we  develop  daily  or 
only  have  a  few  to  develop  now  and  then. 

2.  It  brings  everything  out  that  can  be  got  out  of  an 
underexposed  plate,  and  removes  the  temptation  to  over- 
develop in  the  hope  that  more  details  may  be  obtained. 

3.  It  gives  as  good  results  as  can  be  got  with  overex- 
posed plates,  and  prevents  any  risk  of  insufficient  devel- 
opment which  may  be  caused  by  the  difficulty  of  judging 
how  far  the  development  has  gone  when  the  plate  is  very 
opaque. 

4.  It  reduces  light  fog  to  a  minimum. 

5.  It  overcomes  entirely  the  difficulty  of  determining 
when  development  is  complete. 


CHAPTER  IV 
DEVELOPING  FORMULAS 

Hydrochinon  Formula 

(Tray) 

Water  40  ounces 

Hydrochinon  150  grains 

Sulphite  of  soda  1  ounce,  238  grains 

Carbonate  of  soda  3  ounces,  63  grains 

10%  Solution  Bromide  of  Potassium  40  drops 

Develop  for  7  minutes  at  a  temperature  of  65°  F. 
In   compounding    formulas    avoirdupois   weights    are 
used. 

Metol-hydrochinon  Formula 

(Tray) 

Water  20  ounces 

Metol  (elon,  or  other  substitute)  20  grains 

Sulphite  of  soda  1  ounce 

Hydrochinon  80  grains 

Carbonate  of  soda  1  ounce 

Potassium  bromide  8  grains 

Develop  for  5  minutes  at  65°  F. 

Metol-hydrochinon  Formula 

(Tank) 

Water  1  gallon 

Metol  (or  substitute)  133  grains 
Sulphite  of  soda  6  ounces  292  gr. 

Hydrochinon  1  ounce  97  gr. 

Carbonate  of  soda  6  ounces  292  gr. 

Bromide  of  potassium  53  grains 
Develop  for  5  minutes  at  65°  F. 

35 


36  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

As  has  already  been  stated,  the  temperature  of  the 
developer  should  be  as  nearly  65°  F.  as  possible.  How- 
ever, should  it  be  necessary  to  use  a  higher  or  lower 
temperature  than  the  normal,  the  following  rule  will 
prove  useful :  For  each  5  degree  F.  increase  in  tempera- 
ture, the  developing  time  should  be  decreasd  33%  per 
cent;  for  each  5  degree  F.  decrease  in  temperature,  the 
time  should  be  increased  33l/s  per  cent.  The  following 
table  should  be  copied  and  hung  up  where  it  can  be  readily 
seen : 

Developing  Time    (Metol-liydro- 
Temperalure  cliinon  developer] 

60°  F 6  minutes,  40  seconds 

61°  F 6        "         20       " 

62°  F 6        "  " 

63°  F 5        "         40 

64°  F 5        "         20 

Normal  65°  F 5 

66°  F 4        "         40 

67°  F 4        "         20 

68°  F 4        "  " 

69°  F 3        "  '      40       " 

70°  F 3        "         20 

The  Fixing  Bath 

The  plain  fixing  bath  (hyposulphite  of  soda,  4  parts; 
water,  1  part)  has  little  to  recommend  it.  Its  keeping- 
qualities  are  poor  and  the  bath  has  to  be  made  fresh 
every  day.  It  discolors  rapidly.  An  acid  bath  is  to  be 
recommended  for  all  radiographic  work,  because  it  re- 
mains clear  and  fixes  clean  after  long-continued  use.  In 
the  succeeding  pages  formulas  are  given  for  three 
classes  of  acid  baths. 

No.  1  is  a  plain  acid  bath  having  no  hardening  influ- 
ence. It  is  economic,  will  keep  best  of  the  three  and  is 


DEVELOPING   FORMULAS  37 

excellent  for  use  where  the  temperature  of  the  bath  can 
be  kept  under  70°  F. 

No.  2  has  a  moderate  hardening  influence  on  the  emul- 
sion and  is  intended  for  use  where  the  temperature  is 
not  very  high  but  where  some  hardening  action  is  de- 
sired. 

Xo.  3  has  a  decided  hardening  influence  on  the  emul- 
sion and  is  designed  for  use  in  hot  climates  where  a 
rapid  hardening  of  the  emulsion  is  desirable. 

For  best  results  the  fixing  bath  should  be  kept  acid. 
This  can  be  tested  with  litmus  paper. 

No.  1.  Plain  Acid  Fixing  Bath 

(Tank) 

Water  6  gallons 

Hypo  25  pounds 

When  fully  dissolved  add  the  following  solution: 
Water  1/2  gallon 

Sodium  bisulphite      4  pounds 

No.  2-A.  Acid  Fixing  Bath 

(Tank) 

Water  6      gallons 

Hypo  12%  pounds 

When  fully  dissolved  add  the  following  hardening  so- 
lution : 

Water  i/2  gallon 

Sulphite  of  soda        1  pound 
Acetic  acid  (Xo.  8)  3  pounds 
Powdered  alum          1  pound 

No.  2-B.  Acid  Fixing  Bath 

(Small  Tank  or  Tray) 
Water  64  ounces 

Hypo  16  ounces 


38  DEVELOPMENT    OF    X-EAY    PLATES   AND    FILMS 

When  fully  dissolved  add  the  following  hardening 

solution : 

Water  5  ounces 

Sulphite  of  soda        1  ounce 
Acetic  acid  (No.  8)  3  ounces 
Powdered  alum  1  ounce 

No.  3.  Chrome  Alum  Fixing-  Bath 

(Tank) 

A  B 

Water  96  ounces     Water  32  ounces 

Hypo  2  pounds     Chrome  alum         2  ounces 

Sulphite  of  soda    2  ounces     Sulphuric  acid, 

C.  P.i/i  ounce 

(Mix  chemicals  in  order  named) 

When  dissolved,  pour  B  into  A  slowly  while  stirring 
rapidly. 

Washing 

When  plates  are  fixed  they  should  be  washed  in  run- 
ning water  for  twenty  minutes  or  half  an  hour  to  remove 
all  traces  of  hypo.  If  any  hypo  remains  in  the  emulsion, 
the  negative  will  eventually  fade  or  become  discolored. 

Drying  the  Negative 

Too  great  care  can  not  be  taken  in  the  drying  of  a 
plate,  and  often  a  well-developed  plate  is  spoiled  by  care- 
less drying. 

Plates  are  best  dried  in  a  moderately  warm  room,  hav- 
ing a  fairly  constant  temperature.  They  should  be 
placed  on  end,  not  close  together,  on  a  negative  rack 
somewhat  similar  to  that  shown  in  Fig.  11.  Films  should 
be  attached  to  dental  film  clips  (Fig.  12)  and  hung  up  on 
a  line  to  dry.  See  Fig.  13.  It  is  not  advisable  to  lay 
them  on  a  cloth  pad,  because  in  time  such  a  pad  will  be- 


DEVELOPING   FORMULAS 


39 


come  contaminated  with  chemicals  and  trouble  will  arise. 
In  cold  weather  do  not  allow  the  negative  to  get  too  cold 
while  drying.  If  the  negative  is  partly  dry  and  then  re- 
moved to  another  room  which  is  much  warmer  or  colder, 
it  will  cause  a  difference  in  the  density  of  the  part  to 
drv  last. 


Fie.    11. 


Fig.    12. 

A  negative  may  be  dried  rapidly  with  an  electric  fan, 
but  care  must  be  taken  to  avoid  water  marks. 

If  a  negative  is  wanted  in  a  hurry  it  may  be  dried  rap- 
idly by  laying  it  for  ten  minutes  (after  thoroughly  wash- 
ing) in  a  bath  of  alcohol,  and  then  standing  it  up  to  dry. 


40 


DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 


It  will  dry  in  a  few  moments.    If  dried  in  this  manner 
the  negative  must  first  be  thoroughly  washed,  because 


if  there  is  a  trace  of  hypo  in  the  emulsion  an  insoluble 
white  deposit  will  form  which  will  ruin  the  plate. 


CHAPTER  V 

ALTERATION  OF  THE  NEGATIVE  BY  CHEMICAL 

MEANS 

In  a  previous  chapter  I  pointed  out  the  fallacy  of 
forcing  the  development  of  an  underexposed  plate,  or  of 
shortening  the  development  of  an  overexposed  plate.  To 
prolong  development  will  add  nothing  in  the  way  of  de- 
tail, while  to  shorten  development  means  a  loss  of  both 
detail  and  contrast.  Development  should  always  be  car- 
ried to  a  point  where  there  is  a  complete  reduction  of 
the  detail  portion  of  the  silver  salts  to  their  metallic 
form.  Unless  it  is  carried  to  that  point  much  of  the  ex- 
posed silver  bromide  Avill  not  be  acted  upon  by  the  devel- 
oper and~  will  subsequently  be  lost  in  the  fixing  bath, 
whereas  if  it  is  carried  beyond  that  point  even  the  tin- 
exposed  silver  bromide  will  be  acted  upon  by  the  devel- 
oper, resulting  in  a  heavy  fogged  negative  in  which  the 
details  are  largely  obscured.  All  negatives  should  there- 
fore be  developed  for  a  definite  length  of  time,  regard- 
less of  exposure,  and  errors  of  exposure  should  be  cor- 
rected after  development  by  reduction  or  intensification, 
as  the  case  may  be. 

Intensification 

Negatives  which  show  detail,  but  are  not  dense  enough, 
can  be  intensified  in  the  following  solutions: 

No.  1 

Bichloride  of  mercury  200  grains 

Bromide  of  potassium  200  grains 

Water  10  ounces 

No.  2 

Sulphite  of  soda  %  ounces 

Water  4  ounces 

41 


42  DEVELOPMENT    OF    X-EAY    PLATES    AND    FILMS 


Fig.   14. 


ALTERATION   OF   NEGATIVE   BY    CHEMICAL   MEANS          43 


Fig.  15. 


44  DEVELOPMENT    OF    X-RAY    PLATES   AND    FILMS 

After  the  negative  is  well  fixed  and  thoroughly 
washed,  immerse  it  in  No.  1  until  it  has  become  thor- 
oughly whitened,  and  after  rinsing  carefully  place  it  in 
No.  2,  leaving  it  there  until  full  density  has  been  at- 
tained. In  case  sufficient  intensification  has  not  been 
gained,  wash  for  ten  minutes,  repeat  the  operation  and 
finally  wash  well.  If,  after  intensification,  the  negative 
is  too  dense  it  may  be  reduced  by  placing  it  for  a  few 
seconds  in  water  16  ounces,  hypo,  1  ounce.  If  left  in  the 
hypo  too  long  the  negative  will  be  reduced  to  its  original 
density. 

Fig.  14  shows  a  print  from  an  underexposed  but  nor- 
mally developed  negative.  Owing  to  the  thinness  of  the 
original  negative  there  is  a  lack  of  contrast,  and  the  bril- 
liancy so  much  desired  in  a  plate  or  print  is  largely  lost. 

In  Fig.  15  we  have  a  print  from  the  same  negative 
after  intensification.  The  improvement  is  marked.  The 
general  flatness  of  the  first  print  has  disappeared  and  an 
added  brilliancy  is  the  result. 

However,  intensification  is  usually  less  successful  and 
consumes  more  time  than  reduction  and  we  would  sug- 
gest that  all  badly  underexposed  negatives  be  retaken 
whenever  possible  and  that  intensification  be  resorted  to 
only  where  a  retake  is  not  expedient. 

Reduction 

Negatives  which  are  too  dense  all  over,  due  to  over- 
exposure,  or  to  overexposure  and  overdevelopment, 
should  be  reduced  with  Farmer's  Reducer,  as  follows: 

A 

Water  16  ounces 

Hyposulphite  of  Soda         1  ounce 

B 

Water  16  ounces 

Red  prussiate  of  potassium      1  ounce 


ALTERATION    OF    NEGATIVE    BY    CHEMICAL    MEANS          45 

As  solution  B  is  affected  by  light,  the  bottle  containing 
it  should  be  of  amber  color  or  wrapped  in  opaque  paper 
and  kept  in  the  dark  when  not  in  use. 

Mix  for  immediate  use: 

A  8  ounces 

B  1  ounce 

Use  in  subdued  daylight. 

The  negatives  can  be  transferred  to  this  solution  di- 
rect from  the  fixing  bath  without  rinsing.  The  action 
is  very  rapid  and  must  be  watched  closely.  To  avoid 
streaks,  always  rinse  the  negative  before  holding  it  up 
for  examination.  When  sufficient  reduction  has  taken 
place,  wash  the  negative  thoroughly  in  running  water. 

Negatives  that  have  been  dried  should  be  soaked  in 
water  for  half  an  hour  before  reduction. 

When  parts  of  a  negative  are  too  dense  they  can 
easily  be  reduced  by  applying  the  reducing  solution  to 
those  parts  with  a  tuft  of  cotton,  gently  rubbing  until 
the  desired  reduction  is  attained.  Wash  in  running 
water  frequently  during  the  operation,  taking  care  not 
to  allow  the  solution  to  run  over  the  parts  that  do  not 
need  reduction. 

Farmer's  Reducer  is  necessary  in  every  darkroom. 
By  using  this  reducer,  negatives  which  were  so  dense  as 
to  be  worthless  have  been  made  into  some  of  the  best 
x-ray  negatives  I  have  ever  seen. 

Fig.  16  represents  a  badly  overexposed  but  correctly 
developed  negative.  The  opacity  is  so  great  that  the  de- 
tails are  practically  hidden,  while  the  flesh  tones  have 
entirely  disappeared. 

Fig.  17  shows  the  same  negative  after  reduction  with 
Farmer's  Eeducer.  The  negative  is  now  rich  in  detail. 
The  cancellous  structure  of  the  bone  is  clearly  brought 
out,  even  the  finger  nails  and  delicate  folds  of  the  skin 
are  to  be  seen. 


46 


DEVELOPMENT    OF    X-RAY    PLATES   AND    FILMS 


ALTERATION    OF    NEGATIVE    BY    CHEMICAL    MEANS          47 


48  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

Persulphate  Reducer 

Plates  which  are  too  dense  in  parts,  and  where  all  the 
detail  in  the  shadows  must  be  retained,  can  be  reduced 
as  follows : 

A 

Water  16  ounces 

Persulphate  of  ammonia  %  ounce 

Sulphuric  acid  5  drops 

B 

Water  16  ounces 

Sulphite  of  soda  1  ounce 

After  the  negative  is  well  washed  to  remove  the  hypo, 
place  it  in  Solution  A.  AVhen  reduction  begins,  which 
should  be  in  about  two  minutes,  a  slight  turbidity  will 
be  noticed  in  the  solution.  Watch  the  negative  closely 
and  when  sufficient  reduction  has  taken  place  transfer 
the  negative  for  three  minutes  to  solution  7?  to  stop  the 
reducing  action.  Wash  for  ten  minutes  and  dry. 


CHAPTER  VI 
TANKS 

It  may  be  well  to  add  a  brief  chapter  on  the  various 
kinds  of  tanks  commonly  used  for  photographic  purposes 
and  the  method  of  using  and  caring  for  them.  A  great 
variety  of  tanks  are  manufactured  for  the  developing  of 
glass  plates,  but,  so  far  as  I  know,  only  one  tank  has 
been  designed  for  dental  films.  Since  the  tAvo  kinds  differ 
markedly  let  us  discuss  them  separately. 

Plate  Tanks 

The  plate  tanks  designed  for  photographic  purposes 
are  all  based  on  the  same  mechanical  principles  and  it 
will  therefore  be  unnecessary  in  this  brief  monograph  to 
describe  more  than  one.  In  Fig.  18  is  shown  a  simple, 
yet  practical,  tank  for  the  development  of  glass  plates. 
It  consists  of  a  metal  box  somewhat  larger  than  the 
plate  to  be  developed.  An  inside  plate  rack  is  provided 
to  hold  from  one  to  a  dozen  plates.  This  rack  is  loaded 
in  the  darkroom,  after  which  it  is  lowered  into  the  tank, 
wrhich  has  previously  been  filled  with  the  developing  so- 
lution. The  lid  is  now  clamped  on  and  development  pro- 
ceeds for  a  definite  length  of  time,  depending  upon  the 
temperature  and  the  developer  used. 

In  tank  development  the  negatives  are  not  examined 
during  development  and  there  is  no  risk  of  incorrectly 
judging  their  density.  Density  is  determined  by  the 
length  of  time  of  development,  and  the  length  of  time 
of  correct  development  is  determined  solely  by  the  tem- 
perature and  strength  of  the  developer.  The  tank  should 
be  reversed  or  shaken  several  times  during  development 
to  insure  even  development. 

49 


50  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

Film  Tanks 

An  ingenious  tank  for  the  small-sized  dental  films  is 
shown  in  Fig.  19.  The  tank  is  made  to  hold  eight  small 
metal  tubes,  each  tube  accommodating  a  pair  of  films. 


(See  Figs.  20  and  21.)     The  following  simple  directions 
are  furnished  by  the  manufacturers : 

When  the  tubes  are  loaded,  place  them  in  the  tank  and 
when  all  are  in  position,  pour  in  the  developer.  Six 
ounces  of  solution  is  sufficient  for  developing  eight  pairs 


TANKS 


51 


Fig.  19. 


Fig.  20. 


52 


DEVELOPMENT    OF    X-RAY    PLATES   AND    FILMS 


of  films  at  one  time,  and  as  temperature  is  an  important 
factor  in  film  developing,  the  use  of  a  thermometer  will 
be  found  indispensable  for  ascertaining  the  correct  work- 
ing temperature  (65°  F.)  of  the  solution.  (Two  types 
of  thermometer  are  shown  in  Fig.  22.)  Now  replace  the 
cover  on  the  tank,  securing  it  in  position  by  turning  it 
to  the  right  as  far  as  it  will  go. 


Fig.  21. 

White  light  may  now  be  turned  on  in  the  room  and  the 
time  noted.  With  a  developing  solution  used  at  the  tem- 
perature of  65°  F.,  as  advised,  the  films  should  develop 
for  seven  minutes.  During  this  time  reverse  the  tank 
end  for  end  several  times,  to  insure  even  development 
of  the  films  within. 


TANKS 


53 


2 


Fig.  22. 


54 


DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 


At  the  expiration  of  the  seven  minutes,  remove  the 
cover  from  the  tank  and  pour  off  the  developer,  taking 
care  when  doing  so  to  keep  the  tubes  containing  the  films 


Fig.  23. 


within  the  tank.  Refill  the  tank  with  fresh  water,  in 
which  the  films  must  be  thoroughly  rinsed  before  fixing. 
Several  changes  of  water  should  be  given  them  in  this 


TANKS 


55 


manner,  after  which  the  tubes  should  be  taken  from  the 
tank  and  the  films  removed  from  them  and  placed  im- 
mediately in  the  fixing  solution.  Do  not  place  the  tubes 
in  the  fixing  solution  as  the  chemicals  will  corrode  the 
metal. 

The  Author's  Tanks  for  Dental  Films 


These  tanks  (Fig.  23)  are  made  of  glass,  and  measure 
2y2  X  4  X  6!/2  inches.    They  are  known  as 


' i  rectangular 


Fig.  24. 


specimen  jars,"  and  although  they  are  designed  for  an 
entirely  different  purpose,  they  make  excellent  tanks  for 
the  developing  and  fixing  of  dental  films.  Each  tank  has 
a  capacity  of  20  ounces,  and  by  keeping  the  tanks  well 
filled  and  properly  covered  when  not  in  use,  the  solu- 


56  DEVELOPMENT    OF    X-RAY    PLATES   AND    FILMS 

tions  will  keep  until  exhausted.  The  films  are  attached 
in  pairs  to  dental  film  clips,  and  these  are  hung  over  the 
sides  of  the  tank.  Needless  to  say,  the  films  must  be 
placed  back  to  back,  to  prevent  the  emulsions  from  stick- 
ing. ^:11S1 
To  obtain  the  best  results  the  tanks  should  be  arranged 
on  what  may  be  termed  the  "unit"  system.  In  this 
method  the  developing  and  fixing  tanks  are  placed  in  a 
specially  built  sink  which  is  so  arranged  that  it  may  be 
filled  with  circulating  water.  The  temperature  of  this 
water  should  be  kept  as  near  the  normal  as  possible  by 
combination  hot  and  cold  water  faucets  or  ice.  A  design 
for  such  a  sink  is  suggested  in  Fig.  24.  It  is  constructed 
of  galvanized  iron  and  measures  12  X  12  X  16.  It  is  made 
purposely  deep  so  that  larger  tanks  can  be  accommo- 
dated when  glass  plates  are  to  be  developed.  The  over- 
flow should  be  placed  about  10  inches  from  the  bottom. 
A  rubber  hose  leads  from  this  to  the  main  sink.  A  metal 
shelf  should  also  be  constructed  to  hold  the  smaller  tanks, 
which  tanks  should  be  about  three-fourths  submerged. 

The  Care  of  Tanks 

First,  never  use  the  developing  tank  or  cage  for  the 
fixing  of  the  plates.  The  same  may  be  said  of  the  metal 
tubes  furnished  with  the  dental  film  tank.  They  should 
never  come  in  contact  with  hypo. 

Secondly,  thoroughly  clean  the  tank  and  cage,  or 
tubes,  at  least  once  a  week  Avith  hydrochloric  acid,  1 
ounce,  and  water,  10  ounces,  rinsing  the  tank  well  and 
seeing  that  the  solution  has  access  to  all  parts  of  the 
cage,  special  attention  being  paid  to  the  underside  of  the 
corrugations  holding  the  plates. 

The  Tank  as  a  Standard 

Not  infrequently  when  a  radiographer  changes  from 
the  tray  to  the  tank  method  he  will  be  surprised  to  find 


TANKS  57 

that  his  negatives  are  exceedingly  dense,  much  more  so 
than  when  he  was  developing  by  the  tray  method.  This 
is  an  indication,  first,  that  the  plates  were  overexposed, 
and,  second,  that  they  were  underdeveloped  by  the  tray 
method  and,  of  course  normally  developed  by  the  tank 
method.  The  tank  thus  becomes  an  excellent  standard, 
and  even  if  the  radiographer  prefers  to  use  the  tray 
method  of  development  he  should  use  the  tank  occasion- 
ally as  a  means  of  checking  himself  up  on  exposures. 

Controlling  the  Temperature  of  the  Solutions 

We  have  repeatedly  spoken  of  the  importance  of  main- 
taining a  uniform  temperature  during  development.  It 
is  just  as  important  to  observe  the  temperature  of  the 
developer  as  to  use  the  right  quantity  of  the  right  kind 
of  chemicals.  Heat  increases  the  chemical  action  and 
cold  retards,  so  it  is  obvious  that  for  uniform  results 
the  developer  should  always  be  kept  at  a  certain  definite 
temperature.  Experience  has  proved  that  most  develop- 
ing agents  work  best  at  a  temperature  of  65°  F.  A  cold 
developer  will  produce  thin  negatives,  lacking  in  detail, 
whereas  a  warm  developer  will  produce  a  heavy,  flat 
quality  without  proper  gradation.  Hydrochinon  prac- 
tically ceases  to  work  below  60°  F. 

The  simplest  way  to  maintain  a  uniform  temperature 
has  already  been  described  in  the  paragraph  dealing 
with  the  ' '  unit ' '  system  of  tank  manipulation.  Water  of 
the  proper  temperature  is  allowed  to  circulate  freely 
around  the  tanks  at  all  times,  the  temperature  of  the 
water  being  controlled  by  combination  hot  and  cold  water 
faucets.  During  the  summer  months  the  cold  tap  water 
will  often  be  found  at  the  correct  temperature,  but 
where  this  condition  does  not  obtain  ice  should  be  added. 

The  ideal  method  of  maintaining  a  uniform  tempera- 
ture is  to  employ  a  so-called  "constant  temperature 


58 


DEVELOPMENT    OF    X-EAY    PLATES    AND    FILMS 


bath."  Such  an  apparatus  is  controlled  electrically  and 
is  so  constructed  that  the  temperature  never  varies  over 
half  a  degree.  In  Fig.  25  is  illustrated  a  water-bath 
which  can  readily  be  modified  to  meet  the  requirements 
of  the  radiographer.  The  illustration  is  furnished  by 
The  Thermo  Electric  Instrument  Co.,  of  Newark,  N.  J., 
and  the  following  specifications  are  furnished  by  the 
manufacturers : 


: 


Specifications  of  Water-Bath  for  X-ray  Developing 

Copper  tank  surrounded  on  sides  and  bottom  by  an 
inner  and  outer  wall  of  heavy  asbestos  transite;  the 
space  between  the  inner  and  outer  asbestos  wall  is  filled 
with  heat  insulating  material. 

Shelf; — A  bound  galvanized  wire  mesh   shelf  covers 


TANKS  59 

the  Freas  Thermo-Regulator  which  is  near  the  bottom 
of  the  tank. 

This  leaves  a  working  space  above  the  shelf  of 
12  X  18  X  10  inches. 

Range  of  temperature  up  to  65°  C.  or  145°  F. 

Heating  element  consists  of  a  wire-wound  resistance 
plate  situated  beneath  the  bottom  of  the  tank  and  can 
be  easily  removed  if  necessary. 

Cooling  Coil. — A  copper  cooling  coil  can  be  supplied  to 
keep  the  temperature  constant  when  the  room  tempera- 
ture is  above  the  temperature  desired  in  the  bath.  This 
cooling  coil  to  be  connected  with  a  cold  water  supply. 

Regulation. — Freas  bimetallic  thermo-regulator. 

Constancy  to  within  y2°  C. 

Operation. — Merely  attach  to  ordinary  electric  light 
socket. 


CHAPTER  VII 

A  WORD  ON  CHEMICALS 

In  a  work  of  this  kind  it  is  unnecessary  to  go  deeply 
into  the  question  of  chemicals;  at  the  same  time,  I  can 
not  leave  the  question  untouched  because  of  the  lack  of 
judgment  which  many  display  in  handling  chemicals  and 
compounding  formulas. 

It  is  just  as  important  to  use  pure  chemicals  as  it  is 
to  use  the  correct  amounts  and  the  right  kinds  of  chem- 
icals. Only  such  chemicals  should  be  used  as  have  been 
prepared  by  reliable  firms  for  strictly  photographic  pur- 
poses. This  advice  may  seem  unnecessary,  but  it  is  well 
worth  remembering.  I  had  an  experience  which  con- 
vinced me  that  photographic  chemicals  may  vary  con- 
siderably. All  the  chemicals  which  I  use  are  supplied 
by  the  University  Department  of  Chemistry.  During  the 
World  War  there  was  often  a  shortage  of  chemicals, 
and  many  of  the  supplies  which  were  sent  out  by  the 
department  bore  the  label  of  some  obscure  concern 
which  had  sprung  up  as  a  result  of  the  war.  For  several 
months  I  was  obliged  to  use  a  hydrochinon  which  Avas 
made  by  a  munition  manufacturer.  During  this  period 
the  pictures  which  I  produced  lacked  the  contrast  and 
brilliancy  which  one  usually  associates  with  good  pho- 
tographic work,  and  not  until  I  began  to  test  the  chem- 
icals one  by  one  by  a  process  of  elimination  did  I  dis- 
cover that  the  hydrochinon  was  worthless. 

Some  assistants  not  only  are  careless  in  the  choice  of 
chemicals,  but  even  go  so  far  as  to  substitute  one  chem- 
ical for  another.  I  actually  knoAv  of  an  instance  in  which 
the  assistant  in  a  large  institution  used  ordinary  baking- 
soda  (bicarbonate  of  soda)  instead  of  carbonate  of  soda, 

60 


A   WORD   OK    CHEMICALS  61 

evidently  in  the  belief  that  any  kind  of  soda  would  do. 
Had  he  understood  the  rudiments  of  photography  he 
would  have  known  better.  Bicarbonate  of  soda  is  not 
sufficiently  energetic  to  open  the  pores  of  the  film  within 
the  given  time,  and  unless  the  developer  formula  is  re- 
vised so  as  to  call  for  an  increased  amount  of  bicarbo- 
nate, the  chemical  action  will  be  entirely  too  slow.  Only 
a  trained  chemist  should  attempt  to  substitute  one  chem- 
ical for  another  in  photographic  solutions,  and  the  ra- 
diographer who  is  not  so  trained  had  better  stick  to  pure 
chemicals  and  given  formulas. 

With  the  proper  understanding  of  the  function  each 
chemical  performs,  it  is  easier  to  understand  the  neces- 
sity for  maintaining  the  correct  balance  between  the 
various  chemicals.  Some  brands  of  carbonate  of  soda 
contain  caustic  soda  or  caustic  potash  and,  the  quantity 
being  unknown,  the  action  of  the  alkali  can  not  be  defi- 
nitely predetermined.  Impure  sulphites  also  contain 
various  undesirable  chemicals  thus  producing  uncertain 
and  unusually  undesirable  results. 

Dry  or  anhydrous  sulphite  of  soda  is  double  the 
strength  of  the  crystals.  If  crystal  sulphite  is  used,  take 
double  the  quantity  when  the  dry  is  called  for  in  any 
formula.  Sulphite  deteriorates  when  kept  in  partly 
empty  bottles.  It  should  never  be  purchased  in  paper 
cartons,  but  in  glass  bottles. 

Never  dissolve  more  than  enough  sulphite  of  soda  to 
last  one  week,  as  the  solution  has  a  strong  affinity  for 
oxygen,  which  it  takes  up  both  from  the  water  and  from 
the  air,  converting  part  of  the  sulphite  into  Glauber's 
salts  (sulphate  of  soda)  which  produces  yellow  negatives 
and  irregular  stains. 

Solid  Matter  in  Alkaline  Solutions 

When  the  photographic  developer  is  made  up  in  bulk 
and  kept  for  any  length  of  time  a  deposit  of  small  white 


62  DEVELOPMENT    OF    X-RAY    PLATES   AND    FILMS 

flakes  may  form  at  the  bottom  of  the  bottles.  The  inex- 
perienced workman  often  takes  this  as  an  indication  that 
the  developer  was  cither  improperly  mixed,  or  that  it 
has  deteriorated  and  become  useless.  The  fact  of  the 
matter  is  that  such  deposits  can  hardly  be  prevented  in 
alkaline  solutions  containing  sodium  sulphite  and  sodium 
carbonate.  The  flakes  are  substances  formed  by  the  ac- 
tion of  'the  sodas  on  lime  and  magnesium  salts  contained 
in  hard  water  or  by  their  action  on  the  glass,  or  both. 

Sodium  sulphite,  in  solution,  is  rapidly  oxidized  to 
sulphate.  Sulphate  reacts  with  lime  (the  lime  found  in 
hard  water)  to  form  insoluble  calcium  sulphate  (gyp- 
sum). 

Sodium  carbonate  reacts  with  lime  to  form  insoluble 
calcium-  carbonate  (limestone). 

Sodium  carbonate  combines  with  glass  (the  glass  of 
the  bottle)  to  form  sodium  silicate  (water-glass). 

All  of  these  solids  are  harmless  unless  they  happen  to 
settle  on  the  plate  and  prevent  the  developer  from  acting. 
Simply  filtering  the  developer  before  use  is  all  that  is 
needed. 

If  the  Avater  is  not  hard,  that  is,  if  it  contains  no  lime 
salts,  the  flakes  are  due  entirely  to  the  action  of  the  so- 
das on  the  glass.  Hence  filtering  after  standing  is  prac- 
tically always  necessary,  even  if  rain  or  distilled  water 
is  used. 


CHAPTER  VIII 
USEFUL  SUGGESTIONS 

Weights  and  Measures 

In  compounding  photographic  formulas  Avoirdupois 
weights  are  now  commonly  used. 

1.  Avoirdupois  Weight: 

27.34  grains  1  drachm  =         27.34  grains. 

16        drachms  =     1  ounce  437.5     grains. 

16        ounces  1  pound        :  7000        grains. 

An  accurate  photographic  scale  should  be  found  in 
every  darkroom.  In  Fig.  26  is  shown  an  inexpensive 
scale  which  is  sufficiently  accurate  for  all  photographic 
purposes  and  which  will  weigh  from  one  grain  to  two 
ounces. 

The  Metric  System  is  gradually  being  adopted  by 
chemists  and  photographers  and  formulas  are  often 
given  in  metric  as  well  as  avoirdupois  weights. 

2.  Metric  Weight: 

1  Cubic  Centimeter  =     17  minims  nearly. 

3y2  "                     1  drachm. 

28.4  1  ounce. 

50  1  ounce,  6  drachms,        5  minims. 

100  3  ounces,  4  drachms,      9  minims. 

1000  =  35  ounces,  1  drachm,      36  minims. 
1      Liter  «  =  1000  c.c. 

The  unit  of  the  metric  liquid  measure  is  a  cubic  cen- 
timeter (abbreviated  c.c.).  For  all  practical  purposes 
we  may  say  that  one  ounce  is  equivalent  to  30  c.c.  If  a 
formula  should  call  for  8  ounces  of  water,  then,  we  would 
take  240  c.c. 

63 


DEVELOPMENT    OF    X-RAY   PLATES   AND    FILMS 


USEFUL    SUGGESTIONS  65 

Weights  and  Parts 

Frequently  formulas  will  be  found  which  are  given  in 
parts.  When  all  these  parts  are  solids,  there  is  no  diffi- 
culty in  making  up  the  preparations.  Most  formulas  in 
parts  generally  include  some  liquid,  principally  water. 
Thus: 

Metol,  1  part;  sulphite  of  soda,  4  parts;  water,  32 
parts. 

In  such  case,  substitute  grains  for  parts,  and  the 
formula  will  then  read : 

Metol,  100  grains ;  sulphite  of  soda,  400  grains ;  water, 
3200  grains. 

A  fluid  ounce  of  water  weighs  about  437%  grains,  and 
the  above  quantity  of  water  would  then  be  about  7l/2 
ounces. 

Percentage  Solutions 

The  difficulty  about  percentage  solutions  will  disap- 
pear if  the  worker  will  always  bear  in  mind  that  one 
fluid  ounce  of  water  weighs  437 %  grains,  which  is,  of 
course,  equivalent  in  weight  to  one  ounce  avoirdupois. 
It  follows  that  if  one-tenth  that  number  of  grains — 
that  is,  43.75  grains — of  any  ordinary  soluble  chemical 
is  put  into  a  graduate  glass  and  water  added  to  make  up 
one  fluid  ounce,  the  result  will  be  a  10  per  cent  solution. 

In  the  following  table  the  figures  are  worked  out  for 
solutions  of  various  strengths.  If  the  number  of  grains 
indicated  in  the  table  are  taken  and  sufficient  water 
added  to  make  one  fluid  ounce,  it  will  be  found  that  the 
solution  has  the  required  strength. 

For  a  1%  solution  take  4.37  grains. 

"  5%  "  "  21.87  " 

10%  "  "  43.75  " 

"  20%  "  "  87.50  " 

"  30%  "  "  131.25  " 

"  40%  "  "  175.00  " 

"  50%  "  •"  218.75  " 


CHAPTER  IX 

THE  DARKROOM 

While  any  small  room,  which  can  be  made  absolutely 
dark,  may  be  converted  into  a  proper  darkroom,  it  is  im- 
perative to  the  practical  worker  to  have  the  convenience 
of  a  well-arranged  and  well-ventilated  darkroom,  with 
sinks  and  faucets  supplying  clear  water.  The  room 
should  be  conveniently  arranged  and  kept  clean,  well  ven- 
tilated and  at  the  proper  temperature.  Too  many  shelves 
in  the  darkroom  are  undesirable.  A  shelf  for  the  devel- 
oper, one  for  trays  and  one  for  changing  plates  are  prac- 
tically all  that  are  necessary.  If  possible,  the  chemicals 
should  be  stored,  and  the  various  solutions  prepared  in 
a  corner  of  the  darkroom  set  apart  from  the  essential 
portion  of  the  room.  The  object  of  this  is  to  prevent 
gases  and  floating  particles  of  chemicals  from  reaching 
the  negatives  and  unexposed  plates.  The  darkroom 
should  not  be  a  storage  room  for  empty  cans,  old  solu- 
tions and  other  useless  articles  which  are  liable  to  con- 
tribute their  share  to  future  troubles.  The  utmost  clean- 
liness is  absolutely  necessary  in  the  darkroom.  Have 
clean  floors,  shelves  and  sinks,  and  keep  trays,  graduates 
and  all  chemical  apparatus  clean.  Wipe  off  the  shelves 
frequently.  Mop  the  floor;  do  not  sweep  it.  Solutions 
spilled  and  left  to  evaporate  wi\\  leave  crystals  which, 
at  the  least  stir  in  the  air,  will  fly  about  and  cause  trou- 
bles of  various  kinds.  Experience  proves  that  nearly 
all  darkroom  troubles  come  from  carelessness,  impure 
water,  impure  chemicals  and  dirt  in  its  various  forms. 

A  good  darkroom  entrance  is  in  the  form  of  a  zig-zag 
shape  which  effectually  excludes  the  light,  but  permits 

66 


THE    DARKROOM 


67 


free  passage  and  ventilation.  The  diagram  in  Fig.  27 
will  serve  as  an  illustration. 

The  essential  part  of  the  darkroom  is  within  the  heavy 
black  lines. 

The  sliding  door  allows  the  use  of  both  parts  of  the 
room  independently.  The  entire  room  should  be  painted 


MCLI'T, 

Stnk 

S/iefinj  Doo 


/° 


Sfo, 


&jt- 


Fig.  27. 

a  dead  black  or  dark  brown.  The  wall  between  the  x-ray 
room  and  the  darkroom  should  be  lined  with  lead  to  pre- 
vent stray  x-rays  from  penetrating  the  wall,  because 
such  rays  can  easily  pass  through  several  walls  and  fog 
films  and  plates  on  the  other  side.  If  the  entire  wall  can 
not  be  lined  with  lead,  a  lead  plate  should  be  fastened 


68  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

against  the  wall,  and  all  plates  and  films  should  be  han- 
dled back  of  this  plate.  To  further  insure  the  perma- 
nency of  x-ray  plates,  store  all  unexposed  plates  in  a 
lead-lined  box. 

An  electric  fan  is  a  great  convenience  in  the  dark- 
room, both  to  the  operator  and  in  drying  the  negatives, 
preventing  the  latter  from  becoming  too  intense,  which 
would  be  the  case  when  dried  in  a  sultry  or  hot  at- 
mosphere. During  the  hot  season  the  fan  serves  to  keep 
the  room  and  solutions  cool. 

If  the  bottles  are  wrapped  in  flannel  and  kept  moist 
by  placing  them  in  a  shallow  dish  filled  with  cool  water, 
the  draft  from  the  fan  will  cause  a  considerable  fall  of 
temperature  in  their  contents. 

Testing  the  Darkroom  Light 

It  should  be  remembered  that  no  darkroom  light  is 
absolutely  safe,  and  development  should  always  be  car- 
ried on  as  far  from  the  light  as  possible.  If  there  is  any 
doubt  regarding  the  safety  of  the  light  it  can  be  easily 
tested.  Take  an  unexposed  plate,  lay  it  on  the  table 
where  development  is  usually  carried  on,  then  cover  half 
of  it  with  opaque  paper  and  expose  to  the  developing 
light  for  one  minute.  Now  develop  the  plate  in  total 
darkness  for  three  minutes.  If  the  exposed  half  of  the 
plate  is  perfectly  clear  and  shows  no  fog,  the  darkroom 
light  may  be  considered  safe.  If,  however,  there  is  the 
slightest  variation  in  tone  between  the  exposed  and  un- 
exposed portions  of  the  plate,  it  is  an  indication  that  the 
light  is  not  safe,  and  the  lamp  should  be  covered  with 
several  thicknesses  of  orange  postoffice  paper. 


CHAPTER  X 

LANTEEN  SLIDE  MAKING 

Quite  often  the  radiographer  wishes  to  make  slides  of 
certain  negatives  as  illustrations  to  accompany  a  lecture. 
Before  describing  the  various  methods  of  making  such 
slides  from  x-ray  negatives  let  us  briefly  describe  the 
process  of-  lantern  slide  making  in  general. 

A  lantern  slide  is  a  positive  transparency  on  a  glass 
measuring  3^4  X  4  inches.  The  printing  of  the  slide  does 
not  differ  greatly  from  the  printing  of  an  ordinary  pho- 
tograph, either  by  contact  or  enlarging,  and  any  one  who 
can  make  a  good  photographic  print  should  also  be  able 
to  make  a  good  slide.  When  the  plate  has  been  exposed, 
developed,  and  dried,  a  piece  of  opaque  paper  with  a  cen- 
tral cut-out  is  laid  over  the  plate,  and  this  mask  blocks 
out  the  parts  of  the  picture  not  wanted  in  the  slide.  Over 
the  paper  mask  a  piece  of  clear  glass  is  laid  of  the  same 
size  as  the  one  supporting  the  picture,  and  the  two  glasses 
are  firmly  bound  together  by  gluing  a  strip  of  paper 
around  their  edges.  This  cover-glass,  as  it  is  called, 
serves  the  double  purpose  of  holding  the  mask  in  position 
and  protecting  the  film  from  injury. 

A  slide  is  printed  either  by  contact  or  by  projection. 
If  the  negative  is  of  the  same  size  as  the  lantern  plate,  or 
if  a  portion  of  a  large  negative  is  wanted,  contact  print- 
ing is  the  simpler,  but  if  it  is  desired  to  make  an  enlarged 
picture  from  a  small  negative,  or  a  reduced  picture  from 
a  large  negative,  then  the  slide  must  be  made  by  projec- 
tion. 

Contact  Printing 

The  film  or  plate  to  be  printed  is  placed  in  an  ordinary 
printing  frame,  the  lantern  plate  is  laid  over  it,  and  the 

69 


70  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

two  clamped  together,  emulsion  to  emulsion.  An  expos- 
ure is  now  made  in  the  same  way  as  when  making  a  pho- 
tographic print,  the  only  difference  being  that  a  much 
briefer  exposure  is  made.  An  exposure  equivalent  to  the 
burning  of  a  match  at  a  distance  of  three  or  four  feet 
from  the  printing  frame  will  be  found  approximately 
correct.  The  plate  is  now  developed  and  fixed  in  the 
usual  manner. 

Printing  by  Projection 

When  making  a  slide  by  enlargement  or  reduction  it  is 
necessary  to  use  a  projecting  instrument  with  which  to 
throw  an  enlarged  or  reduced  image  upon  the  sensitive 
plate.  A  simple,  yet  practical,  apparatus  is  shown  in 
Fig.  28.  The  negative  to  be  printed  is  inserted  between 
the  illuminant  and  the  lens  and  a  projected  image  is 
thrown  upon  the  easel.  When  the  image  has  been  prop- 
erly focused  and  centered,  the  lantern  slide  plate  is  in- 
serted in  its  holder  and  the  exposure  made.  Such  an  ap- 
paratus must  be  operated  in  a  room  from  which  all  light 
has  been  excluded,  so  that  the  only  rays  of  light  which 
strike  the  plate  shall  come  through  the  camera  lens. 
With  this  apparatus  films  or  plates  of  any  size  up  to  4  X  6 
inches  may  be  reduced  or  enlarged  to  lantern  plate  size. 

A  different  type  of  apparatus  is  shown  in  Fig.  29. 
This  camera  is  designed  especially  for  lantern  slide  work 
and  has  several  advantages  over  the  former  instrument. 
It  consists  of  three  compartments,  the  center  compart- 
ment carrying  the  lens,  the  one  to  the  left,  the  lantern 
plate,  and  the  one  to  the  right,  the  negative.  The  three 
compartments  are  connected  by  bellows.  It  is  therefore 
evident  that  extraneous  light  can  not  reach  the  plate,  and 
the  exposures  can  therefore  be  made  in  broad  daylight, 
a  darkened  room  being  unnecessary.  The  center  com- 
partment is  fitted  with  a  lens  board  which  can  be  re- 


LANTERN    SLIDE    MAKING 


71 


moved  and  placed  in  front  of  the  camera,  thereby  con- 
verting the  instrument  into  an  ordinary  camera.  The 
lantern  slide  back  is  adjustable  in  any  position,  either 
rising  or  oscillating,  in  order  that  any  oblique  lines  in  the 
negative  may  be  brought  into  correct  position  on  the  lan- 
tern slide.  Focusing  is  done  by  means  of  a  heavy  milled 
head  engaging  the  rack  and  pinion  with  locking  device 
for  securing  the  back  in  any  required  position.  The 


Fig.  21 


Fig.  29. 

movement  of  the  center  compartment  is  controlled  by  a 
milled  head  with  lock  nut  for  holding  the  center  section 
securely  in  position.  The  capacity  of  the  camera  is  5x7. 
Other  types  of  instruments  can  be  had  which  will  ac- 
commodate plates  up  to  14  X  17,  but  since  they  are  funda- 
mentally the  same  as  the  two  already  spoken  of,  a  de- 
scription is  unnecessary  here. 


72  DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 

Lantern  Slides  from  X-ray  Negatives 

The  making  of  a  lantern  slide  from  an  x-ray  plate  dif- 
fers somewhat  from  the  making  of  a  slide  from  an  or- 
dinary photographic  plate.  The  reason  becomes  clear 
when  we  realize  that  a  slide  is  a  positive  print,  whereas 
practitioners  in  general  are  accustomed  to  viewing  the 
negative  or  x-ray  plate  itself. 


Fig    30. 

There  are  two  methods  of  making  a  slide  from  an  x-ray 
negative.  We  may  call  these  the  direct  and  the  indirect 
methods. 

The  Direct  Method 

The  direct  method  is  limited  to  small  negatives,  such 
as  dental  radiograms.  It  is  extremely  simple  and  effec- 


SLIDE    MAKING 


73 


tive.  The  film  is  simply  clamped  between  two  cover- 
glasses,  after  which  the  two  are  glued  together  with  a 
binding  strip.  The  one  advantage  of  such  a  slide  is  that 
all  the  details  that  appear  in  the  original  film  must  neces- 
sarily show  up  on  the  screen,  because  there  is  no  chance 
of  losing  or  gaining  contrast,  as  is  often  the  case  when 
printing  a  slide.  Only  films  which  have  been  correctly  ex- 
posed and  correctly  developed  will  prove  fully  satisfac- 
tory for  this  class  of  work.  Fig.  30  represents  a  slide  of 
the  type  described. 


Fig.   31. 

The  Indirect  Method 

The  indirect  method  is  employed  in  all  cases  where  we 
want  to  make  a  slide  from  a  large  negative,  or  from  a 
group  of  small  dental  films.. 

The  films  are  arranged  between  two  pieces  of  clear 
glass,  say  5X7,  and  the  two  are  held  in  an  upright  posi- 
tion by  means  of  a  pair  of  burette  clamps  and  stands. 
An  ordinary  camera  is  now  placed  at  a  suitable  distance 
from  the  films  and  an  exposure  made  in  the  usual  man- 
ner by  means  of  reflected  light.  (See  Fig.  31.)  By  this 


74 


DEVELOPMENT    OF    X-RAY    PLATES    AND    FILMS 


LANTERN    SLIDE    MAKING  75 

means  we  obtain  what  may  be  called  a  master  negative, 
or  more  correctly  speaking,  a  master  positive.  (See  Fig. 
32.)  From  this  master  positive  any  number  of  slides 
may  be  made.  If  care  be  taken  to  make  the  master  posi- 
tive on  a  3%  X  4%  plate,  slides  can  be  made  by  contact 
printing,  and  the  necessity  of  using  an  expensive  enlarg- 
ing or  l«iiei'4|v^jfede .camera  is  thereby  obviated.  The 
finished  slide  is  shown  in  Fig.  33. 


ETE 


Fig.   33. 

The  proper  developing  formulas  for  lantern  slide 
plates  are  given  in  each  package  of  plates ;  otherwise 
the  same  general  photographic  procedure  as  previously 
outlined  will  apply  with  the  exception  that  a  considerably 
greater  quantity  of  red  light  may  be  used  with  safety  in 
the  darkroom.  Care  must  be  exercised  not  to  overex- 
pose or  overdevelop  lantern  slide  plates. 


INDEX 


Accelerator,  17,  18 
Acetic  acid,  37 
Alcohol,  use  of,  39 
Alkali,  purpose  of,  17 
Alum,  37 
Avoirdupois  weight,   63 

B 

Bicarbonate   of  soda,   61 
Bichloride  of  mercury,  41 
Bromide  of  potassium,  18,  41 
Bromine,  action  of,  29 
how  formed,  29 


0 

Cage,  (see  Eack) 
Calcium  carbonate,  62 

sulphate,  62 

Carbonate  of   soda,   17,  18 
Caustic   soda,  61 

potash,  61 

Chemicals,  a  word  on,  60 
Chrome  alum,  38 
Cold  developer,  action  of,  22,  57 
Constant  temperature  bath,  58 
Contact  printing,  69 
Controlling  temperature,    (see  Tem- 
perature) 
Cooling  coil,  59 
Cover-glass,  69 


1) 


Darkroom,   66 

Density,  cause  for  variation,  39 
Dental  film  clips,  38 
Doehn,  story  told  by,  12 
Drying,  38 
rapid,  39 


E 


Electric  fan,  use  of,  39,  68 
Elon,  17 

Emulsion,  definition,  13 
thickness   of,   3  3 


Factorial  method,  29 
Farmer's  reducer,  44 
Film,  defined,  13 
Film  tubes,  50 
Fixing,   19 
Fixing  bath,  acid,  37 

chrome  alum,  38 

plain,  36 

plain   acid,   36 
Flannel,  use  of,  68 
Fluid  ounce,  weight  of,  65 
Fog,  reason  for,  28 
Freas  Thermo-Begulator,  59 

H 

Hyposulphite  of  soda,  19,  36,  37 
Hydrochinon,  17,  35 

formula,  35 
Hydrochloric  acid,  56 


Image,  how  produced,  18 
Intensification,    41 


Lantern  slide,  definition,  69 

direct  method,   72 

indirect  method,  73 

making,   69 
Lead,  use  of,  67 
Lime  in  solution,  62 
Limestone,  62 

M 

Magnesium  salts  in  solution,  62 

Mask,  69 

Master  negative,  75 

positive,  75 
Metol-hydrochinon,  18 

tray  formula,  35 

tank  formula,  35 
Metric  weight,  63 
Monomet,  17 
Mottling,  cause  of,  29 


77 


78 


INDEX 


N 

Negative,  alteration  of,  41 
Negative  rack,  38 


O 


Orange  postoffice  paper,  68 
Orthochromatic,   16 
Overdevelopment,  danger  of,  18 


Percentage   solutions,   65 
Persulphate  of  ammonia,  48 
Persulphate  reducer,  48 
Phenomet,  17 
Photographic   plate,   13 
Photographic  scale,  63 
Photol,  17 

"Photo-Miniature,"  quoted,  34 
Preservative,  18 
Projection,  70 
Projecting  instrument,  70 


R 

Back,  49 

Reducing  agent,  16,  17,  18 

Reduction,  44 

Red  prussiate  of  potassium,  44 

Bestrainer,  18 

Rhodol,  17 

Rocking,  of  tray,  28,  29 


S 

Serchol,  17 

Sink,  56 

Sodium  bisulphite,  37 

Sodium   silicate,  62 

Solid  matter  in  developers,  61 

Stand  method,      (see  Tank),  31 

Sulphate  of  soda,  61 


Sulphite  of  soda,  17,  41 
Sulphuric   acid,   38 


Tanks,  49 

author's,  55 

care  of,  56 

film,   50 

plate,  49 
Tank  method,  31 
Tank  as  a  standard,  56 
Temperature,   controlling,    57 

normal,  28,   36,   57 

rule  for  variation  of,  36 
Testing  darkroom  light,  68 
Transparency,      (see   lantern    slide) 
Tray  method,  20 


U 


Underdevelopment,   tendency   of,    18 
Unit  system,  56 
Useful  suggestions,  63 


Variation  of   temperature,   rule  for, 

36 
Visual     inspection     method, 

Tray   method) 


W 

Warm  developer,  action  of,  22,  57 
Washing,    38 
Water-glass,  62 
Weights  and  measures,  63 
and  parts,  65 

X 
X-ray  plate,  speed  of,  13 


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